Biochemical studies of the structure of bovine dentine phosphoprotein and its role in the mineralization of dentine matrix are proposed. Previous work in this laboratory has dealt with isolation techniques for purified phosphoprotein and on the interaction of this protein with calcium and phosphate ions in solution. The phosphoprotein has been found to induce the formation of hydroxyapatite in an in vitro system which normally yields amorphous calcium phosphate. Preliminary characterization indicates that bovine dentine phosphoprotein is an oligomeric protein. Studies are proposed which would substantiate this result and allow the isolation and characterization of subunits. This subunit structure may be important to its mineral binding properties since a heterotrophic cooperativity of phosphate binding is observed at physiological levels of calcium ion concentration. Ion binding studies are proposed which would cover a wide range of calcium ion concentrations. In addition, the kinetics of calcium-induced conformational changes will be determined by stopped-flow methods. From these studies it is hoped that a unifying theory of phosphoprotein function in the mineralization of dentine may arise. BIBLIOGRAPHIC REFERENCES: Nawrot, C.F., Campbell, D.J., Schroeder, J.K. and Van Valkenburg, M.: Dental Phosphoprotein-Induced Formation of Hydroxylapatite During in Vitro Synthesis of Amorphous Calcium Phosphate. Biochemistry 15:3445-3449 (1976). Krippner, R.D. and Nawrot, C.F. The Distribution of Aspartic Acid Residues in Bovine Dentine Phosphoprotein. J. Dent. Res. (1976), in press.